July 21, 2010 -- Many women who have had a cesarean section delivery -- and some who have had two C-sections -- can safely attempt to deliver vaginally, according to updated guidelines on vaginal birth after cesarean, or VBAC, issued by the American College of Obstetricians and Gynecologists.

"What is new are a couple of key things," says William A. Grobman, MD, an associate professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine, Chicago, and a co-author of the updated guidelines.

Under the new guidelines, women with two previous cesareans and no previous vaginal delivery, women expecting twins, and women with an unknown type of scar from the previous C-sections are now considered reasonable candidates for vaginal delivery, updating guidelines on the topic issued in 2004 and 2006.

"In the times since those guidelines [were issued], new information was available," Grobman tells WebMD, including two large and scientifically sound studies about VBAC.

New VBAC Guidelines: The Back Story

Over the past 40 years, the C-section delivery rate in the U.S. has risen from 5% in 1970 to more than 31% in 2007, write the authors of the guidelines, published as a practice bulletin in the journal Obstetrics & Gynecology.

Behind the rise, according to the authors, are changes in obstetrics practice, such as the introduction of fetal monitoring and a decrease in forceps delivery.

The old saying of "Once a cesarean, always a cesarean" was also at play, the authors say.

But by the 1970s, data were accumulating to support a trial of labor after cesarean, or what doctors call TOLAC. As the number of women who tried to deliver vaginally after a previous C-section rose, so did complications such as uterine rupture.

That triggered a reversal of the trend, with some hospitals no longer offering women TOLAC.

Then, earlier this year, at a National Institutes of Health consensus conference, experts found TOLAC was reasonable for many women and asked professional organizations to help them help women access the option.

New VBAC Guidelines: A Closer Look

In the guidelines, Grobman and his colleagues note that neither an elective repeat C-section nor a trial of labor after C-section are without risk to mother and baby. Both are associated with risks of maternal hemorrhage, infection, operative injury, and other problems.

After evaluation of the evidence, the ACOG experts made updated recommendations, including:

Women with more than one previous C-section may be candidates for a trial of labor. The experts reviewed two large studies that looked at the risk for women with two previous C-sections who attempted labor. One found no increased risk of uterine rupture in women with one vs. multiple previous C-sections, while the other study found the risk increased from 0.9% to 1.8% in women with one vs. two previous C-sections. The experts conclude that the chance of achieving a vaginal birth after C-section seems similar for women with one or more than one C-sections.

Women who have an unknown type of scar from a previous C-section can also be considered for a trial of labor.

Women expecting twins can be offered the trial of labor.

A trial of labor is not recommended in others, including women who are at high risk for complications, such as women with a previous uterine rupture or extensive uterine surgery.

Previous guidelines recommended that resources for emergency C-sections be "immediately available." "That was interpreted to mean all staff, literally immediately available," Grobman says. In the new guidelines, the ACOG recommends that a trial of labor after C-section ideally be done in facilities well staffed to provide immediate emergency care, but that in a facility without immediate staff available, those doctors and patients discuss the resources and staff availability and carefully consider the decision to try labor.

Overall, about 60% to 80% of women who attempt labor after a previous C-section will deliver vaginally, the authors note.

The guidelines should be interpreted correctly, Grobman says. "This is never about saying that these women should have a trial of labor or shouldn't. It is about the offer and having a plan for a trial of labor and the concept of shared decision making and autonomy, and avoidance of coercion, in either direction."

New VBAC Guidelines: Other Opinions

"This is a fresh look at the evidence again," says Salih Yasin, MD, vice chair of the department of obstetrics and gynecology and director of obstetrics and patient safety at the University of Miami Miller School of Medicine, who reviewed the new guidelines for WebMD.

"Based on this extensive evidence, a trial of labor is a reasonably safe procedure [after C-section] as long as safety guidelines are followed," he says. That means choosing the right patient, he says, as well as the right baby and having the optimal setting in terms of staff and support.

"There are slightly increased risks of complications with a trial of labor after C-section, and these could be offset by careful monitoring."

The new guidelines got a favorable response from the International Cesarean Awareness Network (ICAN). In a statement, ICAN's president, Desirre Andrews, says: "ACOG's updated recommendation for VBAC are much more in line with the published medical research and echo what ICAN has stated for years. Less restrictive access to VBAC will lead to lower risks to mothers and babies from accumulating cesareans."

But the health care environment may need to catch up with the guidelines, according to ICAN. In a 2009 survey of more than 2,800 hospitals, ICAN found that 30% had formal policies forbidding VBAC and 20% had no doctors on staff willing to accept a woman planning VBAC.

SOURCES: William A. Grobman, MD, associate professor of obstetrics and gynecology, Northwestern University Feinberg School of Medicine, Chicago.

Obstetrics & Gynecology, August 2010; vol 116.

Salih Yasin, MD, vice chair, department of obstetrics and gynecology; director, obstetrics and patient safety, University of Miami Miller School of Medicine, Miami.